This invention relates to optical devices for illuminating and inspecting the interior of restricted spaces and, more particularly, restricted spaces at a distance.
Numerous devices have been proposed and used for inspecting spaces and/or compartments which are confined in space and/or to which access is difficult or even dangerous. Such devices typically involve the use of any number of combinations of lenses, magnifiers, mirrors, and/or light sources in order to help make the visual field larger, clearer and/or brighter. However, to date, various difficulties have arisen with the devices known in the art--difficulties ranging from insufficient focus, lack of sufficient light or properly directed or focused light, excess or diffused illumination resulting in lack of clarity and reduction of visual contrast, to the inability to adequately access particularly restricted spaces. Furthermore, an adequate device has yet to be disclosed which provides for the illumination and the inspection of restricted areas or objects at a distance, denoted hereinafter as "telescopic inspection."
Early prior art optical devices include various devices which combine a reading glass or magnifying lens with a separate light source supplied adjacent to the lens, so as to illuminate the object or area being viewed through the lens. Examples of such devices are disclosed in U.S. Pat. Nos. 1,814,540 to Bander, 1,884,968 to Bloch, 2,092,672 to Hyatt and 2,503,850 to Smith et al. While these patents each disclose a lens and illumination combination, none provide a system whereby restricted areas or spaces can be accurately viewed, due to the inadequate size and/or configuration of such devices.
Attempts to satisfy such a need have led to the utilization of reflective viewing apparatus comprising reflective surfaces or mirrors, together with a lens and illumination combination, such as that disclosed in U.S. Pat. No. 4,120,563 to Stefanou. However, while these devices may provide for the inspection of objects or areas in a different field of view, they still do not adequately provide for access to confined or restricted areas, and certainly none have provided for the adequate inspection of narrow spaces and/or objects, let alone visual fields at a distance within such narrow spaces.
U.S. Pat. No. 1,292,326 to Jacobson discloses an elongate device for inspecting confined areas, such as the interior of gas engines. This device optionally employs a mirrored attachment in combination with a magnifying lens and lamp; however, the attachment is disposed upon the device so that the rays emitted from the lamp are not directly projected upon the mirror. A significant drawback of this device, as with other similar inspection devices, is that the light is not aimed directly upon the object or area to be viewed. As a result, the illumination may be insufficient or there may be an abundance of misdirected illumination, which can result in lack of visual clarity. Furthermore, while attempts may be made to use the device for telescopic inspection, the resulting insufficient, misdirected, or excess illumination results in even less visual clarity due to the desired longer distance of inspection.
One apparent attempt to overcome the problem of diffused lighting is disclosed in U.S. Pat. No. 2,778,267 to Miller, Jr. A borescope is provided, wherein the light is reflected off of a primary reflective surface into the bore and the resulting image is reflected off of a secondary reflective surface through the lens in the borescope. It may be inferred that because the reflective surface used to project the light is separate from the reflective surface used to inspect the bore, and the resulting light beam is thus directed in a different optical plane than the viewed area, the incidence of diffused light interfering with the observation may be reduced, although such reasoning is not explicitly disclosed in the patent. However, there is only one aperture in the borescope and, thus, the lighting is still directed through the same opening through which the image of the viewed area or surface is received. As a result, there still remains the probable occurrence of surplus or excess illumination, as well as diffused light and scattered or unfocused light rays. Such a result would not necessarily pose a problem if the light did not have to travel far and the object or space to be viewed was relatively close, such as in the instance of viewing the inner surface of a bore, in which case such a configuration would be suitable. However, the possibility of diffused light or inaccurately and non-focused light rays increases with the distance at which inspection is desired, and such a configuration would in no way be suitable for accurate distance or telescopic inspection of any sort.
Thus, although the device disclosed in the Miller, Jr. patent utilizes a combination of light, separate reflective surfaces and the ability to observe confined areas, its abilities are limited to the microscopic inspection, or inspection at a close distance, of an object or surface, such as the inside of a rifle bore, and is not conducive to the telescopic inspection within any similarly restricted area.
Furthermore, the Miller, Jr. device is intended only for the lengthwise, rotational surface inspection of a bore, and the battery end of the device is sized so as to be inserted first into the restricted space. As a result, the battery is necessarily of a size small enough to fit inside a bore, and such a small battery can provide only a limited amount of power. Moreover, because the battery is located at the opposite end of the eye piece and, thus, the aperture for illuminating and viewing is located at least that far from the end to be inserted, the Miller, Jr. device does not lend itself to the inspection of spaces or areas having a depth limited to a distance shorter than that from the battery end to the illuminating/viewing aperture.